This application is a request for support of a symposium entitled "Organophosphates: Chemistry, Fate and Effects", which will be presented in the program of the Division of Agrochemicals of the American Chemical Society during its national meeting in April, 1990. This will be a 2-day symposium with 19 speakers who were selected for their knowledge and expertise in a variety of aspects of organophosphate chemistry and toxicology. The focus of the symposium is the organophosphate anticholinesterases which have wide current applications primarily in agricultural uses and are therefore subjects of numerous acute and chronic exposures to humans occupationally. The symposium is designed to bring together the many diverse areas of current organophosphate research to stimulate discussion among individuals who may not have had the opportunity to conveniently interact before. The initial topic will be chemistry, with discussion of chemical properties and reactivity, environmental stability, and chemistry of actual and potential therapeutic agents. This will be followed by a discussion of fate, with emphasis on disposition and metabolism in mammalian systems. Last will be a discussion of effects including such topics as tolerance and behavioral effects, as well as non- anticholinesterase effects such as immunotoxicity or delayed neuropathy. The symposium will be a unique opportunity to bring researchers together in a forum with organophosphates as the underlying theme, and will promote new understanding and insights into the ramifications on human health of organophosphate exposures.